Steam activation of a dried sewage sludge was studied to produce hydrogen rich gas and sludge char for converting to energy and resources. A batch-type wire mesh reactor was used to study the characteristics of the steam activation. The characteristics of activation product (i.e., producer gas, gravimetric tar, light tar, and sludge char) were identified. With the increase in the steam feed rate, the sludge char decreased but the producer gas increased, having higher gas heating value. And tar generation slightly increased when a small amount of steam was fed, but when the steam feed rate significantly increased, tar decreased because part of the tar was converted into light gas. Hydrogen and carbon monoxide increased with the increase in the steam feed rate. And carbon dioxide, methane, ethylene, and ethane reached their maximum according to different production mechanisms up to decreasing the species. The gradually increase in the steam feed rate resulted in the creation of micropores, which developed to the maximum when the steam flow rate was 14 mL/g min. When excessive steam was supplied, however, micropores sank due to the resulting sintering phenomenon, and the adsorption capacity deteriorated. The sludge char had a mean pore size of 6.229 nm, which is the size of mesopores from which condensible tar (the cause of damage on the device) is properly adsorbed and removed.